Re: Adding smokes and ROR detectors to existing alarm system

[Nomen Nescio <nobody@xxxxxxxxx>]

Dave A. said:

>I purchased a new home about 18 months ago that included a GE Networx
>NX6V2 security system.  The home also has the typical interconnected
>120V smoke alarms required by code.  However, the security system did
>not include any smoke or heat detectors.  I would like to add some new
>smoke and ROR heat sensors to the security system so that I can have
>monitored fire detection.  I have done some research on my own, and I
>understand that the NEC requires FPL 18AWG (minimum) rated fire wire
>for the smoke and heat sensors.

That's a common misconception.  It's not true.  760.57 allows wire size as
small as 26 gauge, though I wouldn't recommend that.  The 18 gauge
restriction only applies to single conductors, not to individual conductors
in a cable.  You discovered this yourself when you located that 22/4 FPLR
cable.

>I also understand that all common
>components (i.e. keypad, sounder, power supply) must use fire rated
>wiring.  The system currently installed does not use any fire rated
>wiring.  So I will need to replace some of the existing runs with fire
>rated wire.

Technically, yes, you are supposed to use fire wire for the keypads,
sounders, and power.  If your job were being inspected, you'd have to.
Whether you feel it's necessary to replace the wire is up to you.  It won't
make your system work any better.

> My question is this, do I also need to use 18AWG wire for
>the keypad runs?  I have seen several vendors selling 22/4 AWG FPLR
>rated fire wire.  Would this be approved by NEC code if used only for
>the keypads?  The 22/4 is considerably cheaper than 18/4 and my runs
>would be short (no more than about 30 ft each.)

See above.  18 gauge wire is not required.  Fire wire is the standard, and
as you see, it comes in 22 gauge cables as well.

You should also check your existing cables to see whether they are CM, CMR,
or CMP.  If so, those cables are legal.  See the cable substitution chart
in 760.61 (D).  Many people don't believe this, but ordinary telephone wire
(CM, CMR) is perfectly legal for fire alarm use.  Before somebody claims
I'm wrong, read that NEC section.

>Also, I would like to include a combo 190 deg heat and ROR sensor in
>the attic.  Any advice on the best placement for this?  I would assume
>centrally located near the highest point inside the attic, but I would
>appreciate any constructive advice.

Yes, put it within 3 feet of the peak of the attic.  You probably will
require more than one, depending on the size of your attic.  Heat detector
placement can be a complicated subject, but roughly, figure you should have
a row of detectors near the peak of the attic, spaced not more than 30 feet
apart and not more than 15 feet from the walls.  You may need more
detectors if the peak of the attic is more than 15 feet from the lower
edge.

Good luck with your project.  Also remember that the fire code requires an
automatic test signal at least once a month from a monitored household fire
system.  Weekly is preferable.

- badenov